Environment Minister Peter Kent broke the news on his return from talks in Durban, where countries agreed to extend Kyoto for five years and hammer out a new deal forcing all big polluters for the first time to limit greenhouse gas emissions.

Canada, a major energy producer which critics complain is becoming a climate renegade, has long complained Kyoto is unworkable precisely because it excludes so many significant emitters.

The right-of-center Conservative government of Prime Minister Stephen Harper, which has close ties to the energy sector, says Canada would be subject to penalties equivalent to C$14 billion (US$13.6 billion) under the terms of the treaty for not cutting emissions by the required amount by 2012.

Environmentalists quickly blasted Kent for his comments.

Kent did not give details on when Ottawa would pull out of a treaty he said could not work. Canada kept quiet during the Durban talks so as not to be a distraction, he added.

Kent said Canada would work toward a new global deal obliging all major nations to cut output of greenhouse gases China and India are not bound by Kyoto's current targets.